Scientists have created a glass fabric with unprecedented flexibility that can act as a power generator for sensors and wearable devices by converting body heat into electricity.
Wearable devices could become a dime a dozen but companies are still trying to figure out how to incorporate batteries to run thinner devices that would make these gadgets even more appealing to consumers.
As manufacturers try to keep sensors and wearable devices to a minimum size, this usually means installing tiny batteries that do not produce enough juice to last a day.
For example, users of Samsung's first edition Galaxy Gear smart watch often complain of the device's poor battery life that barely last a day. The relatively fewer people who use Google Glass also note that they can only get less than eight hours of use from the wearable device.
Instead of traditional battery technology like lithium ion, scientists are looking at fabricating organic-based thermoelectric generators (TE) that are compatible with the human skin.
These bio-compatible power generators are touted to be capable of running applications on wearable devices like smart watches or medical sensors for longer periods without compromising safety and functionality.
A group of researchers at the Korea Advanced Institute of Science and Technology (KAIST) have invented such a TE generator – a glass fabric as thin as a plaster that can generate 40 mW (milliwatts) of electricity, reportedly several tens of times higher than current batteries used in wearables.
The thermoelectric fabric works by measuring the difference between the temperatures of the body and the surrounding air.
The KAIST scientists devised a new screen printing technique that minimizes the loss of body heat while maximizing power output.
To do this, the researchers let semiconductor pastes permeate through a glass fabric mesh which then formed into films only hundreds of microns thick that conduct electricity.
The technique does away with using inorganic substrates like ceramic which decreases power output. Instead, the glass fabric is used as the substrate, making it lighter and more flexible.
The researchers claim that their generator can be bent as much as 120 times to a radius of up to 20 millimeters. This means it can be flexible and sturdy enough to be worn on the wrist or attached to wearable devices that come into direct contact with the skin.
"For our case, the glass fabric itself serves as the upper and lower substrates of a TE generator, keeping the inorganic TE materials in between. This is quite a revolutionary approach to design a generator. In so doing, we were able to significantly reduce the weight of our generator (~0.13g/cm2), which is an essential element for wearable electronics,”
said researcher Byung Jin Cho, in the study entitled
“Wearable Thermoelectric Generator Fabricated on Glass Fabric” published in the journal Energy and Environmental Science.
Screen printing technology is also being tapped by other researchers to overcome the limits of existing battery technology.
A startup called Imprint Energy is working on a combination of zinc and solid polymer electrolytes that can be printed on paper-thin sheets or bended to almost any shape.
These flexible but powerful thermoelectric generators can help wearable devices become truly ubiquitous and accepted not just because they are fancy and stylish, but also because they are unobtrusive and functional.
Manufacturers are taking notice of these developments, even as they develop their own materials for wearable devices, such as graphene in the case of Samsung.